Hydrofoil stabilizer for boat hull



M 14, Wm

B. E. CLARK HYDROFOIL STABILIZER FOR BOAT HULL 2 Sheets-Sheet 1 Filed Aug. 29, 1968 FIG! IHIIH lilu INVENTOR. IQB RUCEE. CLARK ATTOR EY Jilly M; 1970 B. E. CLARK 3,520,267

HYDROFOIL STABILIZER FOR BOAT HULL FiledAug. 29, 1968 2 Sheets-Sheet 2 2 n. .\\\\\\\\\\\\Q R\\\\\\\ 1 7 FIG. 5 FIG. 6

I INVENTOR. BRUCE E. CLARK United States Patent U.S. Cl. 114-126 6 Claims ABSTRACT OF THE DISCLOSURE A hydrofoil stabilizer for a boat hull including a laterally projecting arm pivotally mounted to the boat hull for horizontal adjustment, and a leeboard pivotally mounted upon the arm for swinging movement in a plane converging toward the longitudinal center plane of the boat hull below the hull.

BACKGROUND OF THE INVENTION This invention relates to a stabilizer for a boat hull, and more particularly to a hydrofoil stabilizer.

Hydrofoils are well known in marine art to elevate the boat hull above the surface of the water after the boat has obtained certain minimum speeds in order to reduce the drag on the boat. Furthermore, leeboards are well known in the art for stabilizing boat hulls, such as canoes, in lieu of center boards or keels. Such leeboards function, not only to steady the boat about its longitudinal axis, but also to minimize leeway, particularly on sail boats.

The combination of a hydrofoil and leeboard is also disclosed in US. Pat. No. 1,356,300 issued to M. and T. A. McIntyre on Oct. 19, 1920. However, the hydrofoilleeboards disclosed inthe McIntyre patent are, for the most part, rigidly fixed to the boat hull.

SUMMARY OF THE INVENTION The hydrofoil stabilizer made in accordance with this invention includes a pivotally mounted leeboard which is adapted to be maintained in its normally operative, depending position during movement through the water, but is adapted to swing, when its bottom end engages an obstruction, such as the bottom of a body of water or a beach, to a trailing unobstructed position. In this manner, a boat, such as a canoe, or small sail boat, incorporating this hydrofoil stabilizer can be beached without damaging or breaking the leeboard or leeboards of the stabilizer.

Another feature of this invention is the pivotal mounting of the arm or strut, supporting the leeboard, to the hull, so that the arm and leeboard may swing or pivot as a unit, horizontally to various positions relative to the hull, in order to vary the angle of attack upon the'leeboard. Since the leeboard functions as a hydrofoil, its various adjusted positions either increase the lifting effect or increase the dragging effect of the water upon the leeboard, as designed.

Both the lee-board and the supporting arm are preferably provided with streamlined cross-sections of a type suitable for surface-piercing hydrofoils so that when they are submerged in the water they will create a minimum of drag upon the boat and a maximum of lift.

The hydrofoil stabilizer made in accordance with this invention is also adapted to be easily and detachably mounted upon the hull of a boat.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevation of a small sail boat upon which the hydrofoil stabilizer is mounted, showing the leeboard in operative and inoperative positions;

FIG. 2 is a fragmentary section taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary top plan View of the apparatus disclosed in FIG. 2;

3,520,267 Patented July 14, 1970 FIG. 4 is a section taken along the line 44 of FIG. 2;

FIG. 5 is an enlarged section taken along the line 5-5 of FIG. 2; and

FIG. 6 is an enlarged section taken along the line 6-6 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in more detail, the hydrofoil stabilizer 10 made in accordance with this invention is disclosed in FIG. 1 as being mounted upon a sail boat 11, having an elongated hull 12. Basically the hydrofoil stabilizer 10 includes a bracket in the form of an elongated transverse beam 15, a lateral supporting arm 16 mounted upon the bracket 15 to project laterally outboard from each side of the hull 12, and a leeboard 17 fixed to the outboard end of each of the supporting arms or struts 16. In the drawings, only the portion of the transverse beam 15, the arm 16 and leeboard 17 on the port side of the hull 12 are disclosed, since all of these elements are duplicated and mounted symmetrically about the longitudinal center plane 18 of the hull 12.

The transverse beam 15 is in the form of an elongated plank, or board, having a flat top surface and being slightly longer than the width of the hull 12, so that its ends will project outboard of the hull 12. The beam 15 is secured to the hull 12, in this instance, to the gunwale rails 19, by hook bolts 20.

The supporting arm or strut 16 is elongated and has an inboard end which is pivotally mounted upon the projecting portion of the beam 15 by means of a handle bolt 22. It is preferred that the bottom surface of the inboard end portion of the arm 16 be flat to cooperate with the upper fiat surface of the transverse beam 15 in relative pivotal movement parallel to each other, when the handle bolt 22 is loosened. As best disclosed in FIG. 3, the arm 16 may be pivoted to any desired angular position relative to the transverse beam 15 such as the phantom-line position, by merely loosening and tightening the handle bolt 22.

The outboard end of the arm 16 diverges up and outwardly at an obtuse angle to the main portion of the arm 16 to form an angular bearing plate or member 23. As shown in FIG. 2, the bearing plate 23 is at an angle of approximately to the top of arm 16. Although the top surface of the bearing plate 23 is preferably streamlined as disclosed in FIG. 5, the bottom surface of the plate 23 is flat so that it will bear flush against the mating, flat, inboard bearing surface 24 adjacent the upper end of the leeboard 17. The outboard surface and the remainder of the inboard surface of the leeboard 17 are preferably streamlined as disclosed in FIGS. 5 and 6. I

The upper end portion of the leeboard 17 is pivotally connected to the angular bearing plate 23 by means, such as the pivot bolt 25 and the wing nut 26. The leeboard 17 will be disposed in a swinging or pivotal plane having the same angle with respect to the plane of the supporting arm 16 as the bearing plate 28. When the leeboard 17 is pivotally mounted upon the arm 16, the lower end 28 of the leeboard 17 will depend to a water depth below the bottom of the hull 12, as disclosed in FIG. 2, when the leeboard 17 is in its normal operative position disclosed in solid-lines in FIGS. 1, 2 and 3, that is, in a transverse plane normal to the longitudinal axis of the hull 12.

In the operation of the invention, the hydrofoil stabilizer 10 is normally mounted in its solid-line positions disclosed in FIGS. 1, 2 and 3 upon the boat hull 12. The book bolts 20 are tightened about the gunwale rail 19 in order to fix the transverse beam 15 securely to the boat hull 12. For normal operation, the arms 16 are adjusted to the solid-line position disclosed in FIGS. 2 and 3 so that its longitudinal axis is co-extensive with the longitudinal axis of the transverse beam 15. The wing nut 26 is loosened upon the pivot bolt 25, and the leeboard 17 pivotally adjusted to its solid-line position disclosed in FIGS. 1, 2 and 3, to extend in the same plane as the longitudinal axis of its arm 16 to permit its lower end 28 to penetrate to the greatest water depth. The wing nut 26 is then tightened to firmly hold the leeboard 17 in its operative position for moving through the water within the speed range of the particular boat 11.

However, the adjustment of the wing nut 26 upon the pivot bolt 25 is such as to permit the swinging movement of the leeboard 17 about the pivot bolt 25 when the lower end 28 or any other portion of the leading edge of the center board 17 engages a fixed obstacle, such as the beach bottom 30 (FIG. 1). When the boat 11 is moving towards the shore as shown in FIG. 1, the bottom end 28 of the leeboard 17 will engage the beach bottom 30, to force the leeboard 17 to a trailing position, such as that disclosed in phantom in FIG. 1, or higher so that the lower end 28 will be swung above the level of the bottom of the boat hull 12. In this manner, the boat 12 may be easily beached without damaging or breaking the leeboard 17.

Because of the angular positions of the leeboards 17 on the opposite sides of the hull 12, they will function as hydrofoils as the boat 11 moves forward and tend to lift the hull 12 in the water, reducing the amount of hull surface beneath the water and thereby reducing the drag on the boat 11. This lifting effect may be increased by releasing the handle bolt 22 and moving the arm 16 forward to a position, such as the exaggerated position disclosed in phantom in FIG. 3. In this forward position, there is a greater angle of attack of the water against the bottom surface of the leeboard 17 thereby creating a greater lifting or planing effect upon the leeboard 17. The greater the lifting effect, of course, the greater the reduction of drag upon the hull 12.

The opposite effect may be attained by swinging the arm 16 to a position behind the normal solid-line position of FIG. 3, to reduce the angle of attack and thereby reduce the lifting effect, or even increasing the drag upon the hull 12. Also, by swinging the arm 16 to a position nearly parallel to the hull 12, the boat 11 may be brought closer to a dock for purposes such as boarding or debarking.

As best disclosed graphically in FIGS. 5 and 6, the cross sections of the leeboard 17 and the bearing plate 23, are preferably streamlined in order to reduce the drag upon the stabilizer 10 as these parts move edgewise through the water, and to create lift.

Where heeling of the hull 12 is anticipated, particularly in a said boat 11, the cross sections of the arms or struts 16 may also be streamlined.

The leeboards 17 on opposite sides of the hull 12 function to stabilize the hull 12 against overturning and also to minimize leeway.

Also, because of the heeling of said boat hulls, such as 12, it is preferred that the lower ends 28 of the leeboards 17 project well below the bottom of the hull 12 so that the leeboard 17 upon the windward side of the hull 12 will 6 remain in the water even when the weather rail is ele vated above the leerail of the hull 12. Thus by pivotally mounting the leeboard 17 to the lateral arm 16, the lower ends 28 of the leeboard 17 may depend far enough below the hull 12 to function properly when heeling, and yet will not be damaged when the hull 12 is beached.

It will be understood, of course, that the hydrofoil stabilizer 10, made in accordance with this invention, may be mounted on other types of boat hulls, including sailing canoes (and non-sailing canoes).

What is claimed is:

1. A hydrofoil stabilizer for a boat hull comprising:

(a) an arm having an inboard end and an outboard end,

(b) means mounting said inboard end upon said boat hull so that said arm projects outboard from said hull,

(c) a leeboard having an upper end and a lower end,

(d) said outboard end of said arm comprising a first flat bearing surface disposed in a plane converging below said hull with the longitudinal center plane of said hull,

(e) said upper end of said leeboard comprising a second flat bearing surface,

(f) connecting means pivotally mounting said first and second bearing surfaces in cooperative engagement so that said leeboard may swing in a plane parallel to said converging plane, and

(g) the lower end of said leeboard being below said hull when said leeboard is in its normal operative position in a transverse plane normal to said center plane.

2. The invention according to claim 1 in which said connecting means is adapted to hold said leeboard in operative position while moving through water, but is adapted to permit said leeboard to swing upon the application of a predetermined force to said leeboard.

3. The invention according to claim 1 in which the mounting means for the inboard end of said arm comprises pivot means to permit the pivotal adjustment of said arm in a plane parallel to the the longitudinal axis of said hull and normal to said center plane.

4. The invention according to claim 3 further comprising a bracket, means for detachably mounting said bracket on said hull, said pivot means pivotally connecting said arm to said bracket.

5. The invention according to claim 1 in which the cross section of said leeboard is streamlined.

6. The invention according to claim 1 in which the cross section of said arm is streamlined.

References Cited UNITED STATES PATENTS 1,356,300 10/1920 McIntyre et a1. 114-126 X 2,509,974 5/1950 Jacobs 114-126 2,720,180 10/ 1955 Schertel 114-665 FOREIGN PATENTS 1,392,346 2/ 1965 France.

0 TRYGVE M. BLIX, Primary Examiner US. Cl. X.R. 114-665 

